In the field of transmission apparatuses, there have been known various techniques for improving the characteristics of error correction process for correcting errors in a receive signal. For example, there has been proposed a technique in which a cyclic permutation matrix is arranged so as to satisfy a predetermined weight distribution, and a low density parity check matrix formed to gradually increase the weight of a row is used to achieve efficient erasure correction of data having a short code length (see, e.g., International Publication Pamphlet No. WO 2006/106841). In addition, there has been proposed a technique in which the size of a region of a root matrix is extended and then a nonzero element is moved so that the density of the nonzero element becomes uniform in the extended region to generate a desired parity check matrix at a high speed (see, e.g., Japanese Laid-open Patent Publication No. 2015-103866). Further, there has been proposed a technique for improving the error correction characteristics by setting a large column weight in the column direction of an element matrix corresponding to the end of the bit string of a signal among element matrixes of a spatially-coupled low density parity check code (see, e.g., Japanese Laid-open Patent Publication No. 2016-213701).
It may be possible to improve the error correction characteristics by using the parity check matrix having the large column weight in the column direction of the element matrix corresponding to the end of the bit string of the signal. In this aspect, however, the parity check matrix will contain parts with different column weights. When a difference in column weights in the parity check matrix gets larger, a shift in processing time due to the column weight difference may occur. Thus, a circuit for executing an error correction process may not be easily implemented by a semiconductor device or the like.
Related techniques are disclosed in, for example, International Publication Pamphlet No. WO 2006/106841, Japanese Laid-open Patent Publication Nos. 2015-103866 and 2016-213701, and Sarah Johnson and Gottfried Lechner, “Spatially Coupled Repeat-Accumulate Codes”, IEEE COMMUNICATIONS LETTERS, VOL. 17, NO. 2, February 2013.